Methane or biogas is a colourless, odourless, flammable gas and the main constituent, 85% to 90%, of the piped natural gas that we use in our homes in the UK, Europe and the USA. Methane can be made using simple apparatus and a process known as anaerobic digestion. Anaerobic digestion is one of the most common biological procedures in nature, as the name implies, it means to carry or breakdown in the absence of air. Once you know the principles of this process it is possible to make biogas in small or large quantities from a variety of waste materials. The book describes making an anaerobic digester using an oil drum and a rubber inner tube as the gas storage vessel as well as a larger continuous digester. The book also contains diagrams, list of materials and websites for further reading. The gas produced can be used for cooking and heating and even for running a gas engine.